The present invention is related to an apparatus for multiplex communication. More specifically, the present invention is directed to an improvement in such an apparatus for multiplex communication capable of properly and flexibly accepting arrangement changes of terminating resistance circuits, depending upon differences in grades of vehicles, while increasing an arranging free degree as to the terminating resistance circuits of a bus type network.
In current vehicles, electrical equipments whose operations are controlled by using electric signals are increased. Furthermore, since these electrical equipments own high performance, communications of large amounts of control signals are necessarily required.
Then, since information amounts are increased due to electric signals communicated between such electrical equipments and controller mounted on vehicles, the related cable installing systems for individually installing cables used to transfer signals every electrical equipment own difficulties. That is, since a total number of signal transfer cables is largely increased, the installation works becomes difficult, and at the same time, recovery operations required when failures (e.g., disconnections of cables) happen to occur become difficult.
To solve these difficulties, very recently, such a research has been made so as to reduce quantities of signal transfer cables which are installed in vehicles in such a manner that while communication functions capable of transmitting/receiving information based upon a predetermined communication protocol are provided with a plurality of electric equipments mounted on vehicles, control signals used for these plural electrical equipments are multiplexed with each other and then the multiplexed control signal is transmitted via a commonly-used bus line.
As such an apparatus for multiplex communication, for instance, one apparatus for multiplex communication includes a plurality of hub type joint connectors connecting various sorts of terminal communication equipments, bus lines for constructing a bus type network by connecting these terminal communication equipments and these hub type joint connectors with each other, and terminating resistance circuits of the bus type network.
FIG. 12 and FIG. 13 illustratively show a related joint connector used in the case that bus lines for multiplex communications are connected to a plurality of electrical equipments in a network. This related joint connector is employed so as to control the plural electrical equipments by way of the CAN (Control Area Network) communication, while this CAN communication is popularized as the multiplex communication protocol of networks provided inside vehicles, and this CAN communication protocol is very recently used as the standard vehicle communication protocol.
As illustrated in FIG. 12, this hub type joint connector 1 includes a connector housing 3, connection terminals 5, a printed wiring (circuit) board 7, and a terminating resistance circuit 9. In the connector housing 3, a plurality of connector engaging portions 3a are opened on an upper plane of this connector housing 3. The connection terminals 5 are individually arranged with respect to each of these connector engaging portions 3a. The printed wiring board 7 is stored/provided inside the connector housing 3. In the terminating resistance circuit 9, structural components are mounted on this printed wiring board 7.
Among a plurality of connector engaging portions 3a equipped in the connector housing 3, partial connector engaging portions are used as bus connection ports for connecting multiplex communication-purpose bus lines, whereas the remaining connector engaging portions are used as terminal connection ports for connecting terminal communication equipments.
Electric connections between the connection terminals 5 in each of the connector engaging portions 3a and either bus lines or terminal communication equipments may be carried out via a male connector 11 which is engaged with each of the connector engaging portions 3a, as shown in FIG. 13.
It should be noted that, the terminal communication equipments connected to the connector engaging portions 3a correspond to various sorts of electrical equipments on vehicle which are equipped with interfaces operable in the CAN communications.
The connector housing 3 includes a housing body 15 and a lower cover 16. The housing body 15 has the connector engaging portions 3a on the upper face thereof, and a lower portion of this housing body 15 is opened. The lower cover 15 covers this lower open portion of the housing body. The printed wiring board 7 is stored/held between these housing body 15 and lower cover 16.
Through holes 7b are formed in an insulating board 7a of the printed wiring board 7, through which leads of the connection terminals 5 and leads of electronic components constituting the terminating resistance circuit 9 may be penetrated. Also, a joint circuit is printed by using a copper foil on a rear face of the insulating board 7a. This joint circuit electrically connects the leads to each other, which penetrate these through holes 7b. 
This joint circuit formed on the printed wiring board 7 is such a circuit for electrically connecting the connection terminals 5 of the respective connector engaging portions 3a in order that the terminal connection port is branched to be connected to the bus lines.
Since the respective connection terminals 5, the leads of which penetrate the through holes 7b, are connected to the respective through holes 7b by a soldering manner, both fixing of these connection terminals 5 to the printed wiring board 7 and electric connections between these connection terminals 5 and the joint circuit can be established.
The terminating resistance circuit 9 provided on the printed wiring board 7 corresponds to such a circuit which is connected to the joint circuit in order to avoid an occurrence of a problem. This problem is caused by reflections of signals at terminals of the bus lines in the case that this joint connector 1 is used at the terminals of the bus lines.
As shown in FIG. 14, this terminating resistance circuit 9 includes a first resistor 21, a second resistor 22 series-connected to the first resistor 21, and a capacitor 23. One lead of this capacitor 23 is connected between the first resistor 21 and the second resistor 22, and the other lead thereof is grounded. The capacitor 23 has the substantially same impedance as that of the bus lines. It should also be noted that the capacitor 23 has a function capable of reducing noise.
It should also be understood that another apparatus for multiplex communication on vehicle type has been developed in which the terminating resistance circuit 9 is not provided with the joint connector 1, but is provided on a printed wiring board of a control unit (ECU) for transferring control signals supplied to respective terminal communication equipments in a multiplex communication format to bus lines.
On the other hand, it is preferable to realize such an idea that the plural sets of joint connectors 1 used in the apparatus for multiplex communication on vehicle type may be commonly employed even at different mounting positions of these joint connectors used in various vehicles in order to achieve manufacturing-cost reductions due to mass production.
However, when total quantities of electrical equipments to be mounted are changed and distribution paths of bus lines are changed due to differences in grades of vehicles, there are some cases that positions required to set terminating resistance circuits in these bus lines are accordingly changed.
As a consequence, in order to properly accept changes in mounting positions of terminating resistance circuits, in the related apparatus for multiplex communication on vehicle in which the terminating resistance circuit 9 is mounted on the joint connector 1, or the printed wiring board of the control unit(ECU), although the terminating resistance circuit 9 is mounted, the joint connector 1 is used as only a hub type joint connector, resulting in a waste of the terminating resistance circuit 9.
Also, while two different sorts of printed wiring boards is previously prepared, namely, a printed wiring board equipped with the terminating resistance circuit 9 and another printed wiring board without mounting of the terminating resistance circuit 9 is prepared in advance, these printed wiring boards may be selectively and properly employed in the joint connector 1, or in the control unit, depending upon a variation of mounting positions of this terminating resistance circuit 9.
However, in such a case that the terminating resistance circuit 9 is replaced by new one (for maintenance purpose) due to malfunction and/or characteristic deterioration thereof, and in the case that since a new electrical equipment is additionally provided, the existing electrical equipment is removed, the mounting position of the terminating resistance circuit 9 on the bus lines is changed, there is such a problem that cumbersome works are necessarily required. That is, the joint connector 1 itself which has been set to the vehicle must be completely replaced by another joint connector, and/or must be disassembled so as to replace only the existing printed wiring board by another printed wiring board.